A string trimmer mechanism intended for mounting on the front end of a mowing tractor. The mechanism includes a mounting bracket for attachment to the front end of the tractor; an extension power cylinder pivotally mounted on the bracket and extending laterally of the tractor; a string trimmer carried on the free end of the power cylinder and including a hydraulic motor driving a trimmer dish; and a lift power cylinder pivotally mounted on the bracket and driving a lever pivotally mounted on the bracket and carrying a roller positioned under the extension power cylinder. The string trimmer is moved selectively laterally inwardly and outwardly utilizing the extension power cylinder and is moved selectively upwardly and downwardly utilizing the lift power cylinder. The extension power cylinder, lift power cylinder, and hydraulic trimmer motor are selectively supplied with pressurized hydraulic fluid from a pressurized hydraulic fluid source onboard the tractor. The string trimmer mechanism converts between left hand operation, with the string trimmer positioned on the left side of the tractor, and right hand operation, with the string trimmer positioned on the right side of the tractor, simply by reversing the direction in which the extension power cylinder extends from the mounting bracket and by interchanging the pivotal mounting of the lift cylinder and the lever on the mounting bracket.